Proviral role of human respiratory epithelial cell‐derived small extracellular vesicles in SARS‐CoV‐2 infection

Abstract

Small Extracellular Vesicles (sEVs) are 50–200 nm in diameter vesicles delimited by a lipid bilayer, formed within the endosomal network or derived from the plasma membrane. They are secreted in various biological fluids, including airway nasal mucus. The goal of this work was to understand the role of sEVs present in the mucus (mu‐sEVs) produced by human nasal epithelial cells (HNECs) in SARS‐CoV‐2 infection. We show that uninfected HNECs produce mu‐sEVs containing SARS‐CoV‐2 receptor ACE2 and activated protease TMPRSS2. mu‐sEVs cleave prefusion viral Spike proteins at the S1/S2 boundary, resulting in higher proportions of prefusion S proteins exposing their receptor binding domain in an ‘open’ conformation, thereby facilitating receptor binding at the cell surface. We show that the role of nasal mu‐sEVs is to complete prefusion Spike priming performed by intracellular furin during viral egress from infected cells. This effect is mediated by vesicular TMPRSS2 activity, rendering SARS‐CoV‐2 virions prone to entry into target cells using the ‘early’, TMPRSS2‐dependent pathway instead of the ‘late’, cathepsin‐dependent route. These results indicate that prefusion Spike priming by mu‐sEVs in the nasal cavity plays a role in viral tropism. They also show that nasal mucus does not protect from SARS‐CoV‐2 infection, but instead facilitates it.

Intrinsic factors behind long‐COVID: I. Prevalence of the extracellular vesicles

“…The ECVs in the nasal cavity assist in the intracellular furin‐mediated prefusion of SARS‐CoV‐2 spike protein during viral entry. This mechanism is mainly performed by vesicular TMPRSS2 activity, which makes SARS‐CoV‐2 more likely to enter target cells via the “early,” TMPRSS2‐dependent pathway, rather than the “late,” cathepsin‐dependent pathway 29 . The SARS‐CoV spike protein's interaction with the ACE2 receptor has been demonstrated to be blocked by the cleavage of ACE2 by the disintegrin and metalloproteinase domain‐containing protein 17 (ADAM17) 30 .…”

“…This mechanism is mainly performed by vesicular TMPRSS2 activity, which makes SARS-CoV-2 more likely to enter target cells via the "early," TMPRSS2-dependent pathway, rather than the "late," cathepsin-dependent pathway. 29 The SARS-CoV spike protein's interaction with the ACE2 receptor has been demonstrated to be blocked by the cleavage of ACE2 by the disintegrin and metalloproteinase domain-containing protein 17 (ADAM17). 30 Tetraspanins (Tspans) are a class of transmembrane proteins that bind to other membrane-associated proteins to provide platforms necessary for viral entry.…”

Meet changes with constancy: Defence, antagonism, recovery, and immunity roles of extracellular vesicles in confronting SARS‐CoV‐2

“…Berry et al. also discovered evidence that EVs originating from the mucus of human nasal epithelial cells (mu‐sEV) increased SARS‐CoV‐2 infection of cells (Berry et al., 2022). They demonstrated that SARS‐CoV‐2 exists in both ‘closed’ or ‘open’ states and that, following SARS‐CoV‐2′s binding to ACE2 on mu‐sEV, the activated protease TMPRSS2 on mu‐sEV cleaves the S1/S2 boundary, exposing the structural domain of SARS‐CoV‐2 bound to the cell surface and leaving the S protein in an ‘open’ conformational state prior to fusion.…”

COVID-19 Plasma Extracellular Vesicles Increase the Density of Lipid Rafts in Human Small Airway Epithelial Cells

“…Currently, the investigation of the virus and its long-term effects on lung health continues to be a priority due to its associated comorbidities, resulting in high mortality rates [ 2 ]. The primary infection initiation site is the epithelial mucosa of the upper respiratory tract and lungs, with a clinical presentation consisting of fever, cough, fatigue, and dyspnea [ 3 , 4 ]. SARS-CoV-2 is a 100 nm single-stranded RNA-enveloped virus.…”

“…Its entry into host cells depends on the binding of the viral (S) spike protein to the angiotensin-converting enzyme 2 (ACE2) receptor, which is mainly expressed in alveolar epithelial cells. Later, activation of serine protease TMPRSS2 leads to a cascade of reactions, triggering infection [ 4 , 5 ]. Recent studies have shown that the infectivity of SARS-CoV-2 is heavily dependent on endocytic mechanisms and has been shown to undergo rapid endocytosis in cells expressing abundant levels of ACE2 [ 5 ].…”